Dentary-Squamosal Joint and the Origin of Mammals

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Science  01 May 1970:
Vol. 168, Issue 3931, pp. 573-575
DOI: 10.1126/science.168.3931.573


The dentary-squamosal jaw joint evolved more than once in advanced cynodont therapsids or their descendants, probably as a buttress against the reaction force created at the articulation by the adductor jaw musculature. The multiple origin of this joint suggests that additional criteria are required to separate early mammals from advanced therapsids.